For cooling and air conditioning of motor vehicles, as a rule, compact units, named hereinafter HVAC (heating, ventilation and air conditioning devices), are used, which contain the components necessary for the requirement. One component required within an HVAC unit is the fan, which directs air through the HVAC unit for purposes of treatment, for example purification or conditioning. The air is brought to the fan in recirculation mode from the vehicle interior, in fresh-air mode from the vehicle exterior, or in mixed mode in the form of a mixture of fresh and recirculated air. Along with mechanical power at the impeller, the electric motor also generates waste heat, which as a rule is removed by means of air circulation. For this, on the compression side of the fan, an interface is inserted into the air flow, which delivers the amount of air necessary for cooling the motor. The heated air then flows out of the electric motor back to the suction side of the fan.
High air velocities along with the arrangement and geometry of the HVAC interface to the cooling air channel of the motor very often result in tonal effects, which have a negative impact on the acoustic properties of the air conditioner. In most cases, interfaces that have straight edges or corners are used, which in the air flow lead to more or less severe disturbances and, often associated therewith, to tonal effects.
JP 2008 203502 A describes a fan in which a portion of the air flowing in an output passage of a spiral-shaped air flow path is directed into an intake opening of a cooling air passage through an air supply channel, which—proceeding from an air inlet opening—is uniformly curved in an S shape. Since the air supply channel—proceeding from the intake opening of the cooling air passage—has an S shape with a plurality of curves, only little resonance noise that is generated in the cooling air passage emerges through the air supply channel into the output passage. The fan is thereby intended to reduce disturbing resonance noises from the cooling air passage and simultaneously ensure a sufficient air volume for motor cooling.
The object of the invention is to define a geometry of the HVAC interface to the cooling air passage of the fan which has as little negative impact as possible on the main airflow, and also does not detrimentally alter the acoustic behavior, if possible. Additionally, it is the goal to supply the cooling air passage to the fan with the required air quantity under all operating conditions if possible, and as much as possible to prevent dirt and moisture from penetrating.